The different colours of oly bushes normally refer to the different shore of the polyurethane, with black being the highest shore (stiffest bush). The yellows are the ones most people fit for the TCA to ARB location.

The standard rubber bushes are terrible, they wear within a very short time and cause very bad judder under braking. Normally the standard bushes are mounted with 2 big washers, the back one is flat and the front one is dished. Some people say that the standard bushes work fine as long as you use the flat washers on both sides of the rubber bush. I haven't tried this myself, so I can't comment on how it compares to poly bushes.